Blend of styrene copolymer with a graft-copolymer of styrene and an alkyl methacrylate upon an alkyl acrylate polymer



United States Patent santo Chemical Company, St. Louis, Mo., acorporation of Delaware No Drawing. Filed Apr. 24, 1959, Ser. No.808,565 8 Claims. (Cl. 260-455) This invention relates to novel graftcopolymers and to blends of said graft copolymers with otherthermoplastic polymers.

It is an object of this invention to provide novel graft copolymers.

Another object of this invention is to provide blends of novel graftcopolymers with other thermoplastic polymers.

ther objects and advantages of the invention will be apparent from thefollowing detailed descriptions thereof.

A novel group of graft copolymers has been prepared by polymerizing20-200 parts of a styrene-alkyl methticrylate monomer charge in anaqueous dispersion containing 100 parts of a rubbery acrylate esterpolymer. A novel group of polymer blends has been prepared by admixingthe above described graft copolymers with certain rigid styreneinterpolymers, preferably styrene-alkyl methacrylate interpolymers, insuch proportions that the rubbery acrylate ester polymer substrate ofthe graft copolymer constitutes about 40% by Weight of the polymerblend.

The following examples and descriptions are set forth to illustrate moreclearly the principle and practice of this invention to those skilled inthe art. Unless otherwise noted, where parts or quantities arementioned, they are parts or quantities by weight.

ACRYLATE ESTER LATEXES A-K A series of latexes of acrylate esterpolymers are prepared employing the polymerization recipe set forthbelow.

Components: Parts Water 300 Monomers 100 Sodium lauryl sulfate 3.0

Potassium persulfate 0.1

3,041,308 Patented June 26, 1962 Table I Monomer Charge Acrylate EsterLatex Identification n-Butyl Aerylate GRAFT COPOLYMER A -W A series ofgraft copolymers are prepared by charging a styrene-methylmethacrylatemonomer mixture (containing 0.2% of dodecyl mercaptan as amodifier) to one of the above prepared acrylate ester latexes whichcontains 100 parts of the rubbery'acrylate ester polymer. The reactionmixture is stirred for 18 hours at C. at the end of which time all ofthe added monomers have polymerized. Two percent of a styrenated phenolantioxidant and 0.2% of a polymerization short stop (both percentagesbeing based on the acrylate ester substrate) are added to the aqueouspolymer dispersion. The acrylate ester latex employed, the quantity ofstyrene-methyl methacrylate monomer charge and the composition of thestyrene-methyl methacrylate monomer charge are set forth in Table II.

Table II Parts of Composition of Styrene Monomer Charge Acrylate MethylGraft Copolymer Ester Metha- Identification Substrate crylate PercentMonomers Percent Methyl Employed Styrene Methacrylate 73 27 55 73 27 7073 27 85 73 27 50 73 27 6O 73 27 8O 73 27 60 50 50 G0 67 33 60 85 15Aliquots of each of the above described graft copolymers are recoveredfrom the latexes by drum drying and arestiff rubbers which exhibitexcellent stabilitywhen exposed to ultraviolet light and/or 'ozone.- Theefficiency of the grafting reaction 'is high asapproxirnately 80% of thecharged styrene-methyl methacrylate monomers polythrough T andrecovering the mixed polymers therefrom by drum drying.Thestyrene-methyl methacrylate interpolymer contains about 73% styreneand 27% methyl methacrylate and has an intrinsic viscosity of about 0.5as determined in dimethylformamide at 25 C. The proportions of resinsolids employed in the preparation of each of the blends are such thatthe rubbery acrylate ester polymer substrate of the graft copolymerconstitutes 30% by weight of the blend. The composition of the blends isset forth in Table III.

Injection molded samples of all of the above polymer blends have anIzod'Impact Strength of greater than 1.0 ft. l-b./inch of notch(measured with a notch having a radius of curvature of 0.01"), a.Tensile Strength of greater than 4,500 p.s.i. and a Flexural Modulus ofgreater than 2.5 X p.s.i. The polymer blends all show excellentstability When exposed to ultraviolet light and/or ozone. a

Part B.For purposes of comparison, 11 control polymer blends areprepared by blending a latex containing 70 parts of the styrene-methylmethacrylate interpolymer described in Part A above with a latexcontaining 30 parts of one of rubbery acrylate ester polymers A throughK I tained with the polymer blends of Part A above.

EXAMPLE II Three additional polymer blends are prepared by the procedureof Example I. The first blend consists, of 48 parts of Graft Copolymer Uand 52 parts of an interpoly- V .mer of 50% styrene and 50% methylmethacryl'atejThe second blend consists of 48 parts of Graft CopolymerVand 52 parts of an interpolymer of 67% styrene and 33% methylmethacrylate. The third polymer blend consists of 48 parts ofGraft'Copolymer W and 52 parts of an 'interpolyrner of 85% styrene and 15% methyl methacrylate. In each of the above blends the proportions ofthe -two polymers are such that the rubbery acrylate ester polymersubstrate of the graft copolymer constitutes 30% by weight of the blend.In each of the blends, the ratio .and recovering the mixed polymerstherefrom by drum 4' of styrene and methyl methacrylate in thesuperstrate of the graft copolymer is identical with the ratio ofstyrene and methyl methacrylate in the styrene-methyl methacrylateinterpolymer.

Each of the above polymer blends has good physical properties includinga high impact strength and has excellent stability when exposed toultraviolet light and/or ozone.

EXAMPLE III.

Example I is repeated except that the styrene-methyl methacrylatecomponent is replaced with an interpolyrner of about 73% styrene and 27%acrylonitrile which has an intrinsic viscosity of about 0.5 asdetermined in dimethylformamide at 25 C. Comparable results areobtained. V

The graft copolymers of the invention are prepared by polymerizing about20-200 and preferably about 20-100 parts by Weight of a styrene-alkylmethacrylate monomer charge in an aqueous dispersion containing 100parts by weight of a rubbery acrylate ester polymer.

The styrene-alkyl methacry-late monomer charge employed in thepreparation of the graft copolymer will consist of about 50-90% byweight of styrene, a ring-alkylstyrene, an alpha-alkylstyrene, analpha-alkyl-, ring-alkylstyrene or a mixture thereof, andcorrespondingly, about 50-10% by weight of at least one alkylmethacrylate in whichthe alkyl group contains 1-4 carbon atoms. Examplesof the ring-alkylstyrenes, alpha-alkylstyrenes, and a1pha-alkyl-,ring-alkylstyrenes which can be employed include o-, m-, andp-methylstyrenes, o-, m-, and p-ethylstyrenes, 2,4-dimethylstyrene,2,4-diethylstyrene, Z-methyl-4-ethylstyrene, alpha-methylstyrene,alpha-ethylstyrene, alpha-methyl-Z-methylstyrene,alpha-methyl-4-methylstyrene, alpha-methyl-2,4-dimethylstyrene and thelike.

To prepare the graft copolymers, the styrene-alkyl methacrylate monomercharge is added to the aqueous dispersion of the rubbery acrylate esterpolymer and the resulting mixture is agitated and heated to atemperature at which the polymerization initiator present in the systeminitiates the polymerization of the added monomers. If

desired, fresh polymerization initiator can be added to thepolymerization system with'the styrene-alkyl methacrylate monomercharge, although this further addition of polymerization initiator isusually not required. In most cases, the residual polymerizationinitiator employed in the polymerization of the rubbery acrylate esterpolymer and/ or the radicals present on the rubbery acrylate esterpolymer chains are sufficient to initiate the polymerization ofthe'added monomers. It is preferred not to add additional emulsifyingagents to the polymerization system and by can'yingout thepolymerization in this manner substantially all of the added monomersbecome dispersed in the previously formed rubbery acrylate ester polymerparticles and the efiiciency of the grafting reaction is very high. Ifdesired, small quantities of polymerization modifiers such as long-chainalkyl mercaptans may be added to the polymerization with thestyrene-alkyl methacrylate monomer'charge so as to regulate and controlthe molecular weight of the final graft copolymer.

The substrates of the graft copolymers are polymers of -100% by Weightof an alkyl acrylate in which the alkyl group contains 2-18 carbon atomsand, correspondingly, 20-0% by weight of a vinylidene monomerinterpolymerizable therewith. Although any alkyl acrylate monomerfalling within the above description can be employed, it is preferred toemploy alkyl acrylates in which the alkyl group contains 2-8 carbonatoms and particularly ethyl acrylate, butyl acrylate and mixturesthereof. Typical vinylidene monomers which can be interpolymerized inminor amounts with the alkyl acrylates include'vinyl chloride,vinylidene chloride, acrylonitrile, methacrylonitrile, alkyl esters ofmethacrylic acid in which the alkyl group contains 1-8 carbon atoms, andthe'like. If desired, small quantities of up to about 1.5%

groups, phosphate partial ester groups and the like.

of cross-linking monomers may be included in the alkyl acrylatepolymers. Cross-linking monomers are monomers containing a plurality ofterminal ethylenic groups which are not conjugated in the1,3 positions.Examples of such cross-linking monomers include divinylbenzene, diallylmaleate, diallyl fumarate, diallyl phthalate, etc.

The aqueous dispersion of the rubbery acrylate ester polymer can beprepared in accordance with any of the usual aqueous emulsionpolymerization procedures known in the art. In general, the monomers areemulsified in water with the aid of micelle-forming emulsifying agentswhich are usually compounds containing hydrocarbon groups of 8-22 carbonatoms coupled to highly polar solubilizing groups such as alkali metaland ammonium carboxylate groups, sulfate half ester groups, sulfonateEremplary emulsifying agents include sodium olea.e, sodium stearate, thesodium salts of sulfate half esters of fatty alcohols produced byreduction of the fatty acids of natural oils such as coconut oil, sodiumabietate, sodium salts of sulfosuccinic esters such as sodium dioctylsulfosuccinate, sodium salts of alkylated benzene and naphthalenesulfonates such as sodium dodecylbenzene sulfate, sodium salts ofmonosulfated fatty acid monoglycerides and the like. Such emulsifyingagents normally will be employed in the ratio of about 2-7 parts per 100parts of monomers. The polymerization medium will contain a suitablewater-soluble, free radical generating polymerization initiator such ashydrogen peroxide, potassium or sodium persulfates, per-borates,peracetates, percarbonates and the like, which polymerization initiatorsmay be associated with activated systems such as redox systems involvingversivalent metals and mild reducing agents. The polymerization mediumalso may contain a chain transfer agent such as a higher alkyl mercaptanof the order of dodecyl mercaptan. The polymerizations can be carriedout at temperatures from about 40 C. to about 80 C. or, in the case ofactivated systems, at temperatures of C. to 80 C.

The graft copolymers of the invention vary in physical nature from stiffrubbers to hard resins. They may be used per se in the manufacture ofmolded articles or may be employed as stiifening and reinforcing agentsin rubber stocks, e.g., in high abrasion resistant shoe sole stocks. Thegraft copolymers also may be used in the manufacture of glass fiberreinforced thermoplastic laminates of the type described in US.2,805,181. be included in blends with hard rigid vinyl chloridepolymers, e.g., polyvinyl chloride, to improve the impact strengththereof. Typically such blends will contain 80-95% by weight of thevinyl chloride polymer and, correspondingly, 20-5% by weight of thegraft copolymer.

A prime utility of the graft copolymers lies in the preparation ofblends with rigid styrene interpolymers. The graft copolymer and therigid styrene interpolymer are admixed in such proportions that therubbery acrylate ester polymer substrate of the graft copolymerconstitutes about -40 or preferably 20-35% by weight of the polymerblend. Such blends can be employed in the manufacture of high strengthmoldings, in the manufacture of extruded sheets and in the manufactureof high strength articles by other methods well-known to the art.

The rigid styrene interpolymers employed in the polymer blends consistof about 50-90% by weight of styrene, a ring-alkylstyrene, analpha-alkylstyrene, an alpha-alkyl-, ring-alkylstyrene, or a mixturethereof and, correspondingly, about 50-10% by weight of acrylonitrile,methacrylonitrile, an alkyl methacrylate in which the alkyl groupcontains 1-4 carbon atoms, or a mixture thereof. Thering-'alkylstyrenes, the alpha-alkylstyrenes, and the alpha-alkyl-,ring-alkylstyrenes that may be included in the rigid styreneintterpolymers are the same as those which may be included in thesuperstrate of the graft copolymers and which have been set forthearlier herein.

They also may 1 6 Such rigid styrene interpolymers can be prepared bymass, solution, suspension or emulsion polymerization techniques bymethods well-known in the art, e.g., see Styrene Its Polymers Copolymersand Derivatives by Boundy and Boyer, Reinhold Publishing Company,Waverley Press, Baltimore, Maryland. Preferably, the rigid styreneinterpolymers employed will have a molecular weight of atleast about30,000. In the preferred polymer blends, the monomer composition of thesuperstrate of the graft copolymer will be substantially identical withthe monomer composition of the rigid styrene interpolymer.

The polymer blends can be prepared by blending latexes of the graftcopolymer and the rigid styrene interpolymer and recovering the polymersfrom the mixed latexes. Alternatively, the polymer blends can beprepared by comalaxating a mixture of the rigid styrene interpolymer andthe graft copolymer at an elevated temperature for a period of timesufiicient to prepare an intimate fusion blend of the polymers.

An outstanding characteristic of both the graft copolymers per se andthe blends of the graft copolymers with the rigid styrene interpolymersis that they have Outstanding resistance to the deteriorative action ofultraviolet light and/or ozone. Accordingly, these compositions may beemployed advantageously in the manufacture of fabricated plasticarticles that are to be exposed to outdoor Weathering conditions.

If desired, conventional compounding ingredients such as colorants,dyes, pigments, stabilizers, antioxidants, plasticizers and the like maybe incorporated in either the graft copolymers per se or in blends ofthe graft coples are set forth by way of illustration only. Many othervariations and modifications of the invention will be apparent to thoseskilled in the art and can be employed without departing from the spiritand scope of the invention herein described.

What is claimed is:

1. An intimate fusion blend of (A) at least one rigid interpolymer ofSit-% by weight of a chemicallycombined monovinylidene aromatichydrocarbon of the group consisting of styrene, a ring-alkylstyrene, analpha-alkylstyrene, an alpha-alkyl-ring-alkylstyrene, and mixturesthereof and 50-10% by weight of a chemically-combined acrylic compoundof the group consisting of acrylonitrile, methacrylonitrile, an alkylmethacrylate wherein the alkyl radical contains 1-4 carbon atoms, andmixtures thereof and (B) a graft copolymer preparedby polymerizing about20-200 parts by weight of a mixture consisting of about 50-90% by weightof a monovinylidene aromatic hydrocarbon of the group consisting ofstyrene, a ring-alkylstyrene, an alpha-alkylstyrene, analpha-alkylring-alkylstyrene, and mixtures thereof and about 50-10% byweight of at least one alkyl methacrylate wherein the alkyl radicalcontains '1-4 carbon atoms in an aqueous dispersion containing parts byweight of a rubbery acrylate polymer which consists of 80-100% by weightof a chemically-combined alkyl acrylate wherein the alkyl radicalcontains 2-18 carbon atoms and up to 20% by weight of achemically-combined interpolymerizable monovinylidene monomer; saidcomponents A and B being so proportioned that the rubbery acrylatepolymer substrate of the graft copolymer constitutes about '5-40%byweight of the blend.

2. A polymer blend as in claim 1 wherein the rubbery acrylate polymer ispolyethyl acrylate.

3. A polymer blend as in claim 1 wherein the rubbery acrylate polymer isa copolymer of about 25-90% by weight of ethyl acrylate and 75-10% byweight of butyl acrylate.

4. A polymer blend as in claim 1 wherein the rubbery acrylate polymer ispolybutyl acrylate. I

5. A polymer blend as in claim l-in which the rigid 7 interpolymer is aninterpolymer of styrene and methyl methacrylate.

6. A polymer blend as in claim 2 in which the rigid interpolymer is aninterpolymer of styrene and methyl methacrylate.

7. A polymer blend as in claim 3 in which the rigid inter-polymer is aninterpeiymer of styrene and methyl methacrylate.

8. A polymer blend as in claim 4 in which the rigid 7 References Citedin the file of this patent methacrylate.

UNITED STATES PATENTS Hayes Aug. 13, 1957 Green June 24, 1958 Jen Nov.1, 1960 FOREIGN PATENTS 7 Great Britain Sept. 17, 1952 UNITED STATESPATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,041,308 June 26,1962 Massimo Baer It is hereby certified that error appears in the abovenumbered patent requiring correction and that the said Letters Patentshould read as corrected below.

Column 3, Table III, heading of column 4, line 2 thereof,

for 'Stryrene-" read Styrenesame Table 111, column 4, llne 12 thereof,for "46" read 49 column 4, line 26, for "thereof, and" read thereof and,

Signed and sealed this 23rd day of October 1962.

(SEAL) Attest:

ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents

1. AN INTIMATE FUSION BLEND OF (A) AT LEAST ONE RIGID INTERPOLYMER OF50-90% BY WEIGHT OF A CHEMICALLY-COMBINED MONOVINYLIDENE AROMATICHYDROCARBON OF THE GROUP CONSISTING OF STYRENE, A RING-ALKYLSTYRENE, ANALPHA-ALKYLSTYRENE, AN ALPHA-ALKYL-RING-ALKYLSTYRENE, AND MIXTURESTHEREOF AND 50-10% BY WEIGHT OF A CHEMICALLY-COMBINED ACRYLIC COMPOUNDOF THE GROUP CONSISTING OF ACRY LONITRILE, METHACRYLONITRILE, AN ALKYLMETHACRYLATE WHEREIN THE ALKYL RADICAL CONTAINS 1-4 CARBON ATOMS, ANDMIXTURES THEREOF AND (B) A GRAFT COPOLYMER PREPARED BY POLYMERIZINGABOUT 20-200 PARTS BY WEIGHT OF A MIXTURE CONSISTING OF ABOUT 50-90% BYWEIGHT OF A MONOVINYLIDENE AROMATIC HYDROCARBON OF THE GROUP CONSISTINGOF STYRENE A RING-ALKYLSTYRENE, AN ALPHA-ALKYLSTYRENE, ANALPHA-ALKYLRING-ALKYLYSTYRENE, AND MIXTURES THEREOF AND ABOUT 50-10% BYWEIGHT OF AT LEAST ONE ALKYL METHACRYLATE WHEREIN THE ALKYL RADICALSCONTAINS 1-4 CARBONS ATOMS IN A AQUEOUS DISPERSION CONTAINING 100 PARTSBY WEIGHT OF A RUBBERY ACRYLATE POLYMER WHICH CONSISTS OF 80-100% BYWEIGHT OF A CHEMICALLY-COMBINED ALKYL ACRYLATE WHEREIN THE ALKYL RADICALCONTAINS 2-18 CARBON ATOMS AND UP TO 20% BY WEIGHT OF ACHEMICALLY-COMBINED INTERPOLYMERIZABLE MONOVINYLIDENE MONOMER; SAIDCOMPONENTS A AND B BEING SO PROPORTIONED THAT THE RUBBERY ACRYLATEPOLYMER SUBSTRATE OF THE GRAFT COPOLYMER CONSITUTES ABOUT 5-40% BYWEIGHT OF THE BLEND.